Refrigeration control system



April 1, 1941. w. L. McGRATH REFRIGERATION CONTROL SYSTEM 3 Shoa -Sheet 1 Filed Dec. 3, 1938 Fig], 1'.

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(Ittorngg April 1, 1941. w. 1. McGRATH 2,237,261

' REFRIGERATION con-men sYs'rsu I Filed Dec. 3, 19:58 s shuts-sheet 2 IS? I39 FROM EVAPO RATOR FROM EVA PQRATOR inventor lF figofi Willllfimmm JLpMEG-mm WW M April 1, 1941. w. L. McGRATH 2,237,261

REFRIGERATION CONTROL sis'ral Filed Dec. 3, 1938 3 ShQQts-Sheet 3 Patented Apr. 1, 1941 2,237,261 REFRIGERATION con'raor. SYSTEM William L. McGrath, St. Paul,'Minn., assignor to Minneapolis-Honeywell Regulator Company,

Minneapolis,

Minn., a corporation of Delaware Application December 3, 1938, Serial No. 243,808

27 Claims.

This invention relates to a control system for a refrigerating apparatus and particularly to a control system for accomplishing defrosting of the cooling coils of the refrigerating apparatus.

It is an object of this invention to provide a control system for a refrigerating apparatus wherein valve means control the circulation of refrigerant through the cooling coil and wherein the valve means is controlled by space temperature and the defrosted condition of the cooling coil, the arrangement being such that upon a call for cooling the valve means is opened only when the cooling coil has defrosted.

Another object of this invention is to apply the above control arrangement to the cooling coils of a multiple fixture refrigerating apparatus to obtain individual temperature and defrosting control in each fixture even though the cooling fluid is supplied to the various fixtures by a common circulating means.

Still another object of this invention is to apply the above control arrangement to those fixtures of a multiple fixture refrigerating apparatus that require defrosting and to control in a conventional manner those fixtures in which defrosting is not desirable whereby individual temperature control of all of the fixtures may be obtained while defrosting control of only part of the fixtures is afforded, all of the fixtures being supplied with cooling fluid. from a common source.

Further objects of this invention reside in the novel manner in which the above sequences of control are accomplished.

Other objects and advantages of this invention will become apparent to those skilled in the art upon reference to the accompanying specification, claims, and drawings'in which:

Figure 1 is a diagrammatic illustration of one form of this invention applied to a multiple fixture refrigerating system to obtain individual temperature and defrosting control of each fixture,

Figures 2 and 3 are diagrammatic illustrations of valves which may be substituted in the system of Figure 1 for obtaining the desired sequence of control, and

Figure 4 is a diagrammatic illustration of a modified control arrangement wherein individual temperature control of the fixtures is obtained and wherein defrosting control of certain of the fixtures is also obtained.

Referring now to Figure 1, a plurality of fixtures to be cooled are illustrated at II), II, and I2 which may be rooms, walk-in boxes, freezer units, soda fountains, and the like. The fixat the 31 associated with the fixture tures III, II, and I2 are cooled by cooling means in the form of evaporators I3, I4, and I5, respectively. Refrigerant is circulated through the evaporator means I3, I4, and I5 by means of a common refrigerating apparatus generally designated at I6 and which may comprise a compressor I1 operated by a motor I8. Compressed refrigerant is delivered by the compressor I6 through a high pressure line I9 into a condenser and condensed refrigerant is collected in a receiver 2|. Liquid refrigerantflows from the receiver 2I through a liquid line 22 to the evaporators I3, I4, and I5. Evaporated refrigerant is withdrawn from the evaporators I3, I4, and I5 through a suction line 23 by the compressor I6. It is here noted that the evaporators I3, I4, and I5 are connected in a parallel relation to the refrigerating apparatus I6.

The flow of liquid refrigerant through the evaporators I3, I4, and I5 is regulated by the usual expansion valves 25, 26, and 21, respectively.

The circulation of refrigerant through the evaporators I3, I4, and I5 is also controlled by solenoid valves 28, 23, and 30, respectively, located outlet of each evaporator. If desired the circulation of refrigerant through the evaporators I3, I4, and I5 may also be controlled by solenoid valves 3|, 32, and 33, respectively, located inthe liquid lines ahead of the expansion valves leading to the evaporators.

The solenoid valves 28 and 3| of the fixture I0 are controlled by a relay 35, the solenoid valves 29 and 32 of the fixture II are controlled by a relay 36, and the solenoid valves and 33 of the fixture l2 are controlled by a relay 31. The relay 35 associated with the fixture III is controlled by a temperature responsive controller 38 responsive to the temperature within the fixture I0 and a defrosted condition responsive controller 39 responsive to the frost conditions of the evaporator I3. In a like manner the relay 36 associated with fixture I I is controlled by a temperature responsive controller 40 and a defrosted condition responsive controller 4I and the relay I2 is controlled by a temperature responsive controller 42 and a defrosted condition responsive controller 43.

Since the defrosted condition of the evaporators is reflected by the pressure within the evaporators, the defrosted condition responsive controllers 39, 4I, and 43 may be made responsive to the pressures existing within the evaporators I3, I4, and I5, respectively.

The operation of the compressor motor l8 and hence the compressor Il may be controlled by a suction pressure controller 45,responsive'to the pressure on the low pressure side of the refrigerating apparatus and a head pressure controller 46 responsive to the pressure on the high pressure side of the refrigerating apparatus.

The relay 35 associated with the fixture |8 may comprise an operating coil 48 for operating switch arms 48, 58, and with respect to stationary contacts 52, 53, and 54. Upon energization of the operating coil 48 the switch arms 48 58, and 5| are moved into engagement with their respective contacts and when the operating coil 48 is deenergized the switch arms are moved out of engagement with their respective contacts by means of springs, gravity, or other means (not shown). The construction of the relays 36 and 31 of the fixtures II and I2 is exactly the same as that of the relay 35 and accordingly like reference characters for like parts have been utilized.

The temperature responsive controller 38 responding to the temperature within the fixture l8 may comprise a bellows 56 charged with a volatile fiuid for operating a lever 51 against the action of an adjustable tension spring 58, the lever 51 operating a mercury switch 58. For purposes of illustration it is assumed that when the temperature within the fixture |8 rises to 42 the mercury switch 58 is tilted to the closed or on position and when the temperature decreases to 40 the mercury switch is tilted to the open or off position shown in Figure 1. The temperature responsive controllers 48 and 42 responsive to the temperature within the fixtures II and J2, respectively, are in all respects the same as the temperature responsive controller 38 and therefore like reference characters for like parts have been utilized. It is obvious that the temperature responsive controllers 48 and 42 may be adjusted for any temperature setting so that differing temperatures may be obtained in the three fixtures I8, II, and i2 and such is within the scope of this invention.

The defrosted condition responsive controller 39 associated with the fixture l8 may comprise a bellows 6| connected by a pipe 62 between the evaporator l3 and the solenoid valve 28 so as to respond to the pressure within the evaporator l3. The bellows 6| operates a lever 63 against the action of an adjustable tension spring 64. The lever 63 operates contacts 65 and 66 with respect to adjustable stationary contacts 61 and 68. The contacts are so arranged that upon an increase in pressure they are sequentially engaged and upon a decrease in pressure they are sequentially disengaged. For purposes of illustration it is assumed that the contact 66 engages and disengages the contact 61 at lbs. and the contact 66 engages and disengages the contact 68 at 35 lbs. The construction of the defrosted condition responsive controllers 4| and 43 is exactly the same as that of the defrosted condition responsive controller 38 and accordingly like reference characters have been utilized for like parts. For purposes of illustration it is assumed that when the pressure in the evaporators |3, M, and I5 rises to 35 lbs. these evaporators have defrosted so that when the contacts 66 and 68 engage this is anindication of the fact that the evaporators have defrosted.

The suction pressure responsive controller 45 may comprise a bellows 18 connected by a pipe 1| to the suction pressure line 23 for operating a lever 12 against the action of an adjustable tension spring 13. The lever 12 operates a mercury switch 14 and for purposes of illustration it is assumed that the mercury switch 14 is moved to a closed position when the suction pressure increases to 30 lbs. and is moved to an open position as shown in Figure 1 when the suction pressure decreases to 10 lbs. Accordingly the suction pressure is at all times maintained be-- tween 10 and 30 lbs. by the suction pressure responsive controller 45.

The head pressure responsive controller may comprise a bellows 16 connected by a pipe 11 to the high pressure line |8 for operating a lever 18 against the action of an adjustable tension spring 18. The lever 18 operates a mercury switch 88 and for purposes of illustration it is assumed that the mercury switch 88 is tilted to the off position when the pressure on the high pressure side of the refrigerating apparatus increases to 180 lbs.

Power is supplied to the compressor motor II, to the various solenoid valves and to the control system by means of line wires 82 and 83 leading from some source of power (not shown). When the suction pressure rises to 30 lbs., 1:. circuit is completed from the line wire 82 through wire 85, mercury switch 14, wires 86 and 81, mercury switch 88, wire 88, compressor motor l8, and wire 88 back to the other line wire 83. Completion of this circuit causes operation of the compressor l1 and the compressor remains in operation until the suction pressure decreases to 10 lbs., or the pressure on the high pressure side of the refrigerating apparatus increases to 180 lbs. In this manner the compressor I1 is operated to maintain the suction pressure between 10 and 30 lbs. and is shut off in case the head pressure increases to a high value 01' 180 lbs.

Assuming now that the temperature within the fixture |8 rises to 42 to close the switch 58 and that the evaporator |3 has defrosted causing the contacts 66 and 66 to engage the contacts 61 and 68, a circuit is thereupon completed from the line wire 82 through wire 8|, mercury switch 58, wire 82, contacts 61, 65, and 68, wire'83, operating coil 48 and wire 84 back to the other line wire 83. Completion of this circuit energizes the operating coil 48 to move the switch arms 48, 58, and 5| into engagement with the contacts 52, 53, and 54, respectively.

Movement of the switch arm 58 into engagement with the contact 53 completes a circuit from the line wire 82 through switch arm 68, contact 53, wires 85 and 86, solenoidvalve 28, and wires 81 and 88 back to the other line wire 83. Accordingly when the relay 35 is pulled in the solenoid valve- 28 is opened. The solenoid valve 3| is connected in parallel with the solenoid valve 28 by means of wires 88 and I88 and hence when the solenoid valve 28 is opened upon pulling in of the relay 35 the solenoid valve 3| is likewise opened. It follows then that when therelay 35 is pulled in, the evaporator l3 of the fixture I8 is cut-in to the refrigerating system to cool the fixture |8.

Movement of the switch arm 48 into engagement with the contact 52 completes a maintaining circuit for the operating coil 48 which is independent'of the contacts 68 and 68 of the frost condition responsive controller 38, this circuit being traced from the line wire 82 through wire 8|, mercury switch 58, wire 82, contacts 61 and 65, wire |8|,contact 52, switch operating coil 48, and wire 84 back to the other line wire 83. Completion of this maintaining arm 49, wire In,

circuit maintains the solenoid valves 28 and 3| open until either the temperature within fixture I decreases to 40 or the pressure within the evaporator I3 decreases to 15 lbs. When either of these contingencies occur, the solenoid valves 28 and 3| are closed and cannot be again reopened until the temperature within the fixture I0 increases to 42 and the pressur'in the evaporator I3 has increased to 35 lbs. indicating that the evaporator has defrosted. By reason of this arrangement the temperature within the fixture I0 is maintained within desired limits and the evaporator I3 is defrosted each time that the solenoid valves 28 and 3| are closed. Frost free temperature control within the fixture I0 is therefore obtained.

The various circuit connections between the temperature responsive controller 40, the defrosted condition responsive controller 4|, the relay 36, and the solenoid valves 29 and 32 associated with fixture I I and the various circuit connections between the temperature responsive controller 42, the defrosted condition responsive controller 43, the relay 31 and the solenoid valves 30 and 33 associated with the fixture I2 are the same as those outlined above in connection with those of fixture I0 and therefore like reference characters for like circuit connections have been utilized. In other words, the solenoid valves 29 and 32 associated with fixture II and thesolenoid valves 30 and 33 associated with fixture I2 are operated in exactly the same manner as the solenoid valves 28 and 3| associated with fixture I0. Accordingly individual temperature and defrosting control for each fixture is obtained. Any temperature responsive controller can call for cooling and open its associated solenoid valves providing its evaporator is defrosted regardless of whether-the other temperature responsive controllers are calling for cooling or are satisfied.

The switch arm 5| and; the contact 54 of the relays 35, 36; and 31 may be located in parallel with the low pressure responsive controller 45 to cause operation of the compressor I1 when any of the solenoid valves are opened. For example assume that the relay 35 associated with fixture I0 is pulled in to open the solenoid valves 25 to 28, a circuit is completed from the line wire 82 through switch arm 5|, contact 54, wires. I05, I

I06, I01, and 81, mercury switch 80, wire 88, compressor motor I8 and wire 89 back to the other line wire 83. The switch arm 5| and contact 54 of the relay 36 and the switch arm 5| and contact 54 of the relay 31 are located in parallel with the switch arm 5| and contact 54 of the relay 35 by means of wires I08 and' I09, respectively, so that when any of the relays are pulled 'in, the compressor I1 is operated. If this auxiliary switching mechanism is utilized it may be desirable to locate the suction pressure responsive controller in series therewith instead of in parallel. as shown to prevent the suction pressure from decreasing below a predetermined value and such a modification is within the contemplation of this invention. I

Referring now to Figure 2, a valve is generally designated at I I5 and may be substituted for the valves 28, 29, and 30 of Figure 1 to perform substantially the same sequence of operation as is accomplished.- in Figure 1. The valve 5 may comprise a valve casing I I6 divided by a partition 1 into a chamber 8 connected to the evaporator I3 and a chamber ||9 connected to the suction side of the compressor. The partition H1 is provided with a port I20 controlled by a valve I2| to control the communication between chambers H8 and H9. Mounted on the valve casing H6 is another casing I22 provided with a cover I23. Sealed to the casing I22 are concentrically located bellows I24 and I25 which are in turn sealed to a plate I26. The space between the bellows I24 and I25 is connected by a capillary tube I21 to a bulb I28 which may be located within the fixture being cooled. The bulb I28 is charged with a volatile fluid so that the plate I26 is moved upwardly upon an increase in temperature and is moved downwardly upon a decrease in temperature. The plate I26 is connected by a valve stem I28 to the valve I2I so that the valve I2| is moved concurrently with movement of the plate I26. A spring |3I locatedbetween the plate I26 and a spring retainer I32 carried by an adjusting screw I33 is utilized for urging the valve I2I towards its seat. By adjusting the adjusting screw I33 the temperature setting of the instrument may be adjusted at will to maintain desired tempera- ,i'i "-1 ture conditions within the fixture.

A plate I35 suitably secured to the valve casing"; I|6 has sealed thereto one end of a bellows I36, A

the other end being sealed to a plate I31. spring I38 located in the bellows I36 between the plate I31 and a spring retainer I39 carried by an adjusting screw I40 urges the plate I31.;

towards the right. The plate I31 carries an abutment I4I adapted to engage a notch I42 in the valve stem I29. The abutment I4I is guided by a 11 member I43 slidably engaging a lug I44 formed in the valve casing II6. The abutment MI and notch I42 form a latch for holding the valve I2I against the valve seat I20. When the temperature in the fixture increases an upward force on the valve stem I29 is exerted by the plate I26 but the valve I2I cannot open since is latched closed by the abutment |4I engagingthe slot I42. When the evaporator pressure has risen sufficiently to indicate that the evaporator has defrosted the plate I31 is moved to the left to release the abutment |4I from the notch I42 whereupon the valve |2| is opened to cut the evaporator into the refrigeration circuit. Immediately the pressure in the evaporator decreases but the abutment member I4I cannot engage the notch I42 since the notch I42 is not in alignment with the abutment I4| when the valve |2I is opened. When the temperature in the fixture decreases to the desired value the valve I2I is closed and the abutment I4I then engages the notch I42 to latch the valve closed. Accordingly the valve cannot again be reopened upon an increase in fixture temperature until the evaporator has defrosted. In order that the valve I2I may operate freely after the abutment I4I has been released it may be desirable to insert a strain release between the bellows plate I31 and the abutment member I4I. From the above it is seen that the valve mechanism is operated in substantially the same manner as the solenoid valves of Figure l and accordingly the valve mechanism of Figure 2 may be substituted for the valve mechanisms of the system shown in Figure 1.

Figure 3 discloses a valve arrangement for accomplishing substantially the same results as are accomplished by the valve arrangement of Figure 2. The same valve casing and pressure responsive device is utilized in the valve mechanism I50 of Figure 3 as in the valve mechanism I I5 of Figure 2 and accordingly like reference characters have been utilized for like parts. In Figure 3 a plate I52 is secured to the top of the valve casing I I6, the plate being provided with a tube I53 upon which is mounted an operating coil I54. A casing I55 secured to the plate I52 encloses the tube I53 and the operating coil I54. The upper end of the valve stem I29 is provided with a collar I51 engaged by a spring I58 for urging the valve I2I to its seat I20. A spring I59 is interposed between the collar I51 and an armature I60 slidably mounted on the valve stem I29. The spring I59 is stronger than the spring I58 when compressed so that when the armature I 60 is moved upwardly the spring I59 overcomes the spring I58 to open the valve I2I. When the armature I60 drops to the position shown in Figure 3 the spring I58 closes the valve I2I.

The operating coil I54 may be controlled by a temperature responsive controller 38 which may be the temperature responsive controller located in the fixture I of Figure 1. When the temperature affecting the temperature responsive controller rises to a predetermined value, for example 42, the mercury switch 59 is closed to complete a circuit from the line wire I62 through mercury switch 59, wire I63, operating coil I54 and line wire I64. Completion of this circuit energizes the operating coil I54 to move the armature I60 upwardly compressing the spring I59. The valve stem I29 however is prevented from moving upwardly by the latch means formed by the abutment I 4I and the notch I42. When the evaporator has defrosted the abutment member I disengages the notch I42 and the spring I59 opens the valve I2I thereby cutting the evaporator into the refrigeration circuit. Immediately the pressure in the evaporator decreases but the abutment member does not engage with the notch I42 inasmuch as the valve I2I is opened. When the temperature within the fixture decreases, to say 40, the mercury switch 59 is opened to deenergize the operating coil I54 whereupon the armature I60 moves downwardly to the position shown in Figure 3 and the spring I58 closes the valve I2I. Upon closing of the valve I2I the abutment I4I engages the notch I42 to prevent reopening of the valve I2I until the evaporator has defrosted. The purpose of the spring I59 is to allow the armature I60 to move upwardly even though the valve I 2| is latched closed thus preventing overheating of the operating coil I54.

Referring now to Figure 4, two fixtures in which a defrosting action is required are designated at I and "I while a single fixture in which no defrosting is desirable is designated at 112. fixtures I 10 and "I may be rooms, walk-in boxes, or the like while the fixture I12 may be a freezing compartment, ice cream freezer, or the like. The fixtures I10, HI, and I12 are cooled by cooling coils in the form of evaporators I13, I14, and I15, respectively. Refrigerant is circulated through the evaporators by a refrigerating apparatus generally designated at I16 which may comprise a compressor I11 operated by an electric motor I18. The compressor "1 delivers compressed refrigerant through a high pressure line I19 into a condenser I80 and the condensed refrigerant is collected in a receiver I8I. Liquid refrigerant flows from the receiver I8I through a liquid line into the evaporators I13, I14, and I and evaporated refrigerant is withdrawn from the evaporators through a suction line I83 by the compressor I 11. It is here noted that the various evaporators are connected in parallel with respect to each other into the refrigerating system. The circulation of the refrigerant through the evaporators I13, I14, and I15 is regulated by expansion valves I84, I85, and I86, respectively. Solenoid The valves I81, I88, and I89 control the supply of refrigerant to the evaporators I13, I14, and I15, respectively. I

A pressure regulating valve I9I provided with a bypass I92 and a manual valve I93 may be located in the suction line leading from the evaporators I13 and I14 to regulate the pressure existing within these evaporators. A solenoid valve I94 is located between the evaporators I13 and I14 and the pressure regulating valve I9I and when this valve is closed communication between the suction side of the compressor and the evaporators I13 and I14 is interrupted.

The solenoid valves I81, I88, and I89 are controlled by temperature responsive controllers I96, I91, and I98, respectively, responsive to the temperature conditions within the fixtures I10, "I, and I12. The solenoid valve I94 in the suction line leading from the evaporators I13 and I14 is controlled by a relay generally designated at I99 and this relay is in turn controlled by a defrosted condition responsive controller in the form of a suction pressure responsive controller 208 responsive to the pressure in the evaporators I13 and I14 and the temperature responsive controllers I96 and I91 arranged in parallel with respect to each other.

A relay 20I which controls the operation of the compressor motor I18 and hence the compressor I11 is in turn controlled by a head pressure controller 202 responsive to the pressure on the high pressure side of the refrigerating apparatus by a suction pressure controller 203 responsive to the pressure on the low pressure side of the refrigerating apparatus, by the temperature responsive controller I98 in the fixture I12 and by a switch included in the relay I99.

The temperature responsive controller I 96 responding to the temperature within the fixture I10 may comprise a bellows 205 charged with a volatile fluid for operating a lever 206 against the action of an adjustable tension spring 201. The lever 206 operates a mercury switch 208 provided with three electrodes at one end thereof. For purposes of illustration it is assumed that,

when the temperature within the fixture I18 rises to 42 the switch 208 is tilted to a position to cause the mercury therein to bridge the three electrodes and when the temperature within the fixture decreases to 40 the mercury switch 208 is tilted to the open position as shown in Figure 4. The temperature responsive controllers I91 and I98 are exactly like the temperature responsive controller I96 and accordingly like reference characters for like parts have been utilized. It is evident that the temperature responsive controller I91 may respond to different temperature values than the temperature responsive controller I96 and since the fixture I12 is utilized, for example, as a freezing fixture it is evident that the temperature responsive controller I98 will most likely respond to much lower temperatures, say 26 to 28.

The relay I99 which controls the operation of the solenoid valve I94 may comprise an operating coil 2I0 for moving switch arms 2I I, 2I2. and 2I3 into engagement with contacts 2, 2I5, and 2I6, respectively, upon energization thereof. When the operating coil H0 is deenergized the switch arms are moved out of engagement with their respective contacts by means of springs, gravity, or other means (not shown).

The suction pressure responsive controller 208 responding to the pressure within the evaporators I13 and I14 and hence the defrosted condition of these evaporators may comprise a bellows 2" I when the pressure increases to 35 lbs., illustratively, which corresponds to a defrosting temperature.

The relay or starter 224 which controls the operation of the compressor motor I18 and hence the compressor I11 may comprise an operating coil 224 for moving a switch arm 225 into engagement with a contact 226 when energized. When the operating coil 224 is deenergized the switch arm 225 is moved out of engagement with the contact 226 by means of springs, gravity, or other means (not shown).

The suction pressure responsive controller 203 may comprise a bellows 228 connected by a pipe 229 to the suction pressure line I83 adjacent the compressor I11 for operating a lever 230 against the action of an adjustable tension spring 23I. The lever 230 opens a mercury switch 232 when the pressure on the low pressure side of the refrigerating apparatus decreases to, illustratively, lbs.

The head pressure controller 202 may comprise a bellows 234 connected by a pipe 235 to the high pressure line I19 for operating a lever 236 against the action of an adjustable tension spring 231. The lever 236 opens a mercury switch 238 when the pressure on the high pressure side of the refrigerating apparatus increases to,'illustratively, 180 lbs.

Power is supplied to the compressor motor I18, the various solenoid valves and to the control system by means of line wires 240 and 24I leadin from some source of power (not shown).

Assume now that the temperature within the fixture E12 rises to 28, to close the mercury switch 208, a circuit is thereupon completed from the line wire 240 through wire 242, mercury switch 208, wire 243, solenoid valve I89, and wire 244 back to the other line wire 24I. Completion of this circuit opens the solenoid valve I89 to permit circulation of refrigerant through the evaporator I15. Closing of the mercury switch 208 of temperature responsive controller I98 also completes a circuit from the line wire 240 through wire 242, mercury switch 208, wires 245 and 246, mercury switch 238, wire 241, mercury switch 232, wire 248, operating coil 224 of the relay or starter MI and wire 249 back to the other line wire 24!. energizes the operating coil 224 as long as the temperature responsive controller I98 is'calling for cooling, the pressure on the high pressure side of the refrigerating apparatus is below 180 lbs. and the pressure on the low pressure side cf the refrigerating apparatus is above 10 lbs. Energization of the operating coil 224 moves the switch arm 225 into engagement with the contact 226 to complete a circuit from the line wire 240 through wire 250, switch arm 225, contact 226, wire 25I, compressor motor I18 and wire 252 back to the other line wire 24I. Com pletion of this circuit operates thecompressor motor I18 and hence the compressor I11 to circulate refrigerant through the evaporator E to cool the fixture I12. When the temperature within the fixture I12 decreases to 26 the mercury switch 208 is tilted to the open position to close the solenoid valve I89 and to stop operation of the compressor I11.

Completion of this circuit Assume now that the temperature within the fixture I18 rises to 42' to close the mercury switch 288, a circuit is thereupon completed from the line wire 240 through wire 254, mercury switch 208, wire 266, solenoid valve I81, and wire 256 back to the other line wire 24I. Completion of this circuit opens the solenoid valve I81 to permit the flow of refrigerant into the evaporator I13. When the evaporators I13 and I14 are defrosted to allow the pressure therein to rise to 35 lbs. to close the mercury switch 222 of the frost condition responsive controller 200, a starting circuit is completed from the line wire 240 through wire 254, mercury switch 208, wires 251. 258, and 259, mercury switch 222, wire 260, operating coil 2l0, and wire 26I back to the other line wire 24I. Completion of this circuit energiszaes the operating coil 2III to pull in the relay Movement of the switch arm 2I2 into engagement with the contact 2| 5 upon pulling in of the relay I98 completes a circuit from the line wire I 42 through wires 263 and 264, contact 2I5, switch arm 2I2, wire 265, solenoid valve I94, and wires 266 and 26.I back to the other line wire 24I. Completion of this circuit opens the solenoid valve I94 to establish communication between the evaporators I13 and I14 and the suction pressure side of the compressor I11 whereupon refrigerant is allowed to flow through the evaporator I13.

Movement of the switch arm 2I3 into engagement with the contact 2I6 upon pulling in of the relay I99 completes a circuit from the line wire 240 through wires 263 and 268, contact 2 I 6, switch arm 2I3, wires 269 and 246, mercury switch 238, wire 241, mercury switch'232, wire 248, operating coil 224 of the relay or starter -28I and wire 249 back to the other line wire 24I. Completion of this circuit pulls in the relay or starter 20I to operate the compressor I11 as long as the relay I99 is pulled in providing the head pressure ilsobilow lbs. and the suction pressure is above Movement of the switch arm 2 into engagement with the contact 2I4 upon pulling in of the relay I99 completes a maintaining circuit for the operating coil m of the relay I99 which is independent of the mercury switch 22 of the frost condition responsive controller 200. This maintaining circuit may be :traced from the line wire 240 through wire 254, mercury switch 208, wires 251, 258, and 21I, contact 2I4, switch arm 2, wire 212, operating coil 2I8, and wire 26I back to the other line wire 24I. The relay I99 will therefore remain energized until the temperature within the fixture I10 decreases to 40.

Assume now that the temperature within the fixture I1I rises to 42 to close the mercury switch 208. A circuit is thereupon completed from the line wire 240 through wire '214, mercury switch 208 of the temperature responsive controller I91, wire 215, solenoid valve I88, and wire 216 back to the other line wire 24I. Completion of this circuit therefore opens the solenoid valve I88. When the evaporators I13 and I14 are defrosted to allow the pressure therein to decrease to 35 lbs. a starting circuit for the relay I99 is completed from the line wire 24'!) through wire 214, mercury switch 208 of the temperature responsive controller I91, wires 218, 258, and 259, mercury switch 222, Wire 260, operating coil 2l0, and wire 26I back to the other line wire 24I. This starting circuit pulls in the relay I99 to open the solenoid valve I94 and to start the compressor I11 in the manner pointed out above. Upon pulling in of the relay I89 a maintaining circuit therefore is completed through the mercury switch 208 of the temperature responsive controller I 91 to maintain the relay I 99 pulled in until the temperature within the fixture I1I decreases to 40.

From the above it is seen that the temperature responsive controllers I96 and I91 control their respective solenoid valves I81 and I 88 and act in parallel with each other and in conjunction with the frost condition responsive controller 200 to pull in the relay I99 for opening the solenoid valve I94 and for operating the compressor I11. The arrangement of Figure 4 also splits up the refrigerating system into two parts, one part including fixtures having coils which are required to be defrosted and the other part including fixtures wherein defrosting of the coils is not required. In the first part the fixtures are individually controlled in accordance with temperature and it is impossible to circulate refrigerant through the fixtures unless they have been defrosted. In the second part the fixtures are individually controlled but no defrosting action is accomplished. In addition when any fixture demands cooling the compressor is placed in operation to circulate refrigerant through the coil of that fixture and both head pressure and suction pressure protection are provided.

Although for purposes of illustration several forms of this invention have been disclosed other forms thereof may become apparent to those skilled in the art upon reference to this disclosure and therefore this invention is to be limited only by the scope of the appended claims and prior art.

I claim as my invention:

1. In a cooling system including a cooling aoparatus having a cooling coil for cooling a space and means for circulating through the cooling coil a cooling fluid having sufiicient cooling capacity to lower the temperature of the cooliria coil below freezing whereby frosting of the cooling coil may occur, the combination with said apparatus of, valve means for controlling the circulation of cooling fluid through the cooling coil, and control means responsive to the temperature of the space and to a condition normally attendant to a defrosted state of the cooling coil for opening the valve means only upon both an increase in space temperature and the attainment of such condition.

2. In a cooling system including a cooling apparatus having a cooling coil for cooling a space and means for circulating through the cooling coil a cooling fluid having sumcient cooling capacity to lower the temperature of the cooling coil below freezing whereby frosting of the cooling coil may occur, the combination with said apparatus of, valve means for controlling the circulation of cooling fluid through the cooling coil, control means responsive to changes in space temperature for opening and closing the valve means to maintain the space temperature at desired values, and control means responsive to a condition normally attendant to a defrosted state of the cooling coil for preventing opening of the valve means by the temperature responsive control means until such condition is present.

3. In a cooling system including a cooling apparatus having a cooling coil for cooling a space and means for circulating through the cooling coil a cooling fluid having sufllcientcooling capacity to lower the temperature of the cooling coil below freezing whereby frosting of the cooling coil may occur, the combination with said apparatus of, valve means for controlling the circulation of cooling fluid through the cooling coil, control means responsive to changes in space temperature for opening and closing the valve means to maintain the space temperature at desired values, latch means for latching the valve means in a closed position, and means responsive to a condition normally attendant to a defrosted state of the cooling coil for releasing the latch means when said condition is attained.

4. In a cooling system including a cooling apparatus having a cooling coil for cooling a space and means for circulating through the cooling coil a cooling fluid having sufficient cooling capacity to lower the temperature of the cooling coil below freezing whereby frosting of the cooling coil may occur, the combination with said apparatus of, valve means for controlling the circulation of cooling fluid through the cooling coil, electromagnetic means for opening and closing the valve means, a maintaining switch closed upon opening of thevalve means, a first switch, means responsive to space temperature for opening and closing the first switch, a second switch, means responsive to a condition normally attendant to a defrosted state of the cooling coil for closing the second switch when such condition exists, means for completing a starting circuit through the first and second switches and the electromagnetic means to open the valve means, and means for completing a maintaining circuit through the first switch, the maintaining switch and the electromagnetic means to maintain the valve means open until the space temperature decreases.

5. In a refrigeration system including a refrigerating apparatus having evaporator means for cooling a space and a compressor for circulating refrigerant through the evaporator means, the combination with said apparatus of, valve means on the discharge side of the evaporator means for controlling the circulation of refrigerant through the evaporator means, and control means responsive to the temperature of the space and the pressure in the evaporator means for opening the valve means upon an increase in space temperature providing the evaporator means is defrosted.

6. In a refrigeration system including a refrigerating apparatus having evaporator means for cooling a space and a compressor for circulating refrigerant through the evaporator means, the combination with said apparatus of, valve means on the discharge side of the evaporator means for controlling the circulation of refrigerant through the evaporator means, control means responsive to changes in space temperature for opening and closing the valve means to maintain the space temperature at desired values, and control means responsive to the pressure in the evaporator means for preventing opening of the valve means by 'the temperature responsive means until the evaporator means is defrosted.

7. Ina refrigeration system including a refrigerating apparatus having evaporator means for cooling a space and a compressor for circulating refrigerant through the evaporator means, the combination with said apparatus of, valve means on the discharge side of the evaporator means for controlling the circulation of refrigerant through the evaporator means, control means responsive to changes in space temperature for opening and closing the valve means to maintain the space temperature at desired values, latch means for latching the valve means in a closed position, and means responsive to the pressure in the evaporator means for releasing the latch means when the evaporator means is defrosted to prevent opening of the valve means by the temperature responsive control means until the evaporator means is defrosted.

8. In a refrigeration system including a refrigera-ting apparatus having evaporator means for cooling a space and a compressor for circulating refrigerant through the evaporator means, the combination with said apparatus of, valve means on the discharge side of the evaporator means for controlling the circulation of refrigerant through the evaporator means, electromagnetic means for opening and closing the valve means, a maintaining switch closed upon opening of the valve means, a first switch, means responsive to space temperature for opening and closing the first switch, a second switch, means responsive to the pressure within the evaporator means for closing the second switch when the evaporator means is defrosted, means for completing a starting circuit through the'flrst and second switches and the electromagnetic means to open the valve means when the space temperature increases and the evaporator means is defrosted, and means for completing a maintaining circuit through the first switch, the maintaining switch and the electromagnetic means to maintain the valve means open until thespace temperature decreases.

9. In a cooling system including a cooling apparatus having a plurality of cooling coils for cooling a plurality of spaces and a common means for circulating through the cooling coils a cooling fluid having sufllcient cooling capacity to lower the temperature of the cooling coils below freezing whereby frosting of the cooling coils may occur, the combination with said apparatus of, valve means associated with each cooling coil for controlling the flow of cooling fluid through its cooling coil, and control means associated with each cooling coil and responsive to a condition normally attendant to a defrosted state of its cooling coil and the attainment of a predetermined high temperature in the space cooled thereby for opening the valve means of that -cool ing coil.

10. In a cooling system including a cooling apparatus having a plurality of cooling coils for cooling a plurality of spaces and a common means for circulating through the cooling coils a cooling fluid having sufllcient cooling capacity to lower the temperature of th cooling coils below freezing whereby frosting of the cooling coils may occur, the combination with said apparatus of, valve means associated with each cooling coil for controlling the flow of cooling fluid through its cooling coil, control means associated with each cooling coil and responsive to the temperature of the space cooled thereby for opening and closing the valve means of that cooling coil to maintain the space temperatures at desired values whereby individual temperature cont-r01 of each cooling coil is obtained, and control means associated with each cooling coil and responsive to a condition normally attendant to a defrosted state of the cooling coil thereof for preventing opening of the valve means of that cooling coil by the temperature responsive control means until such a condition has been attained.

11. In a refrigeration system including a, refrigerating apparatus having a plurality of evaptherethrough, and control means associated-with each evaporator means and responsive to the pressure therein and to the temperature of the space cooled thereby for opening the valve means of that evaporator means upon an increase in space temperature providing that evaporator means is defrosted whereby individual temperature and defnosting control of each evaporator means is obtained.

12. In a refrigeration system including a refrigerating apparatus having a plurality of evaporator means for cooling a plurality of spaces and a common compressor for circulating refrigerant through all of the evaporator means, the combination with said apparatus of, valve means on the discharge side of each evaporator means for controlling the circulation of refrigerant therethrough, control means associated with each evaporator means and responsive to the temperature of the space cooled thereby for opening and closing the valve means of that evaporator means to maintain the space ternperature at desired values whereby individual temperature control of each evaporator means is obtained, and control means associated with each evaporator means and responsive to the pressure therein for preventing opening of the valve means of that evaporator means by the temperature responsive control means until that cooling coil is defrosted whereby individual defrosting control of each evaporator means is obtained.

13. In a cooling system including a cooling apparatus having-a first cooling coil for cooling a space wherein defrosting of that cooling coil is desirable, a second cooling coil for cooling another space wherein defrosting of that cooling coil is not required and a common means for circulating cooling fluid through both cooling coils, the combination with said apparatus of, valve means for controlling the circulation of coolin fluid through the first cooling coil, and control means responsive to the temperature of the space cooled by the first cooling coil and to a condition normally attendant to a defrosted state of the first cooling coil for opening the valve means upon an increase in space temperature providing said condition has been attained.

14. In a, cooling system including a cooling apparatus having a first cooling coil for cooling a space wherein defrosting of that cooling coil is desirable, a second cooling coil for cooling another'space wherein defrosting of that cooling coil is not required and a common means for circulating cooling fluid through both cooling coils, the combination with said apparatus of, valve means for controlling the circulation of cooling fluid through the first cooling col-l, control means responsive to an increase in the tempcrature of the space cooled by the first cooling coil and to a condition norm-ally attendant to a defrosted state of the first cooling coil for opening the valve means, second valve means for controlling the circulation of cooling fluid through the second cooling coil, and control means responsive to the temperature of the space cooled by the second cooling coil for opening the second valve means upon an increase in space temperature.

15. In a refrigeration system including a refrigeratlng apparatus having a first evaporator means for cooling a space wherein defrosting of that evaporator means is desirable. a second evaporator means for cooling another space wherein defrosting of the evaporator means is not required and a common compressor for circuleiting refrigerant through both evaporator means. the combination with said apparatus of, valve means on the discharge side 'of the'first evaporatormeans for controlling the circulation of refrigerant therethrough, and control means responsive .to the pressure in the first evaporator means and to the temperature of the space cooled thereby for opening the valve means upon'an increase in space temperature providing th firs evaporator means is defrosted.

16. In arefrigeration system including a refrigerating apparatus having a, first evaporator means for cooling a space wherein defrosting of that evaporator means is desirable, a second evaporator means for cooling another space wherein defrosting of the evaporator means is not required and a common compressor for circulating refrigerant through both evaporator means, the combination with said apparatus of, valve means on the discharge side of the first evaporator means for controlling the circulation of refrigerant therethrough, control means responsive to the pressure in the first evaporator means and to the temperature of the space cooled thereby for opening the valve means upon an increase in space temperature providing the first evaporator means is defrosted, second valve means for controlling the circulation of refrigerant through the second evaporator means, and control means responsive to the temperature of the space cooled by the second evaporator means for opening the second valve means upon an increase in space temperature.

17. In a cooling system including a cooling apparatus having a first cooling coil for cooling a space wherein defrosting of that cooling coil is desirable, a second cooling coil for cooling another space wherein defrosting of that cooling coil is not required and a common means for circulating cooling fiuid through both cooling coils, the combination with said apparatus of, valve means for controlling the circulation of cooling fluid through the first cooling coil, controi means responsive to an increase in the temperature of the space cooled by the first cooling coil and to a condition normally attendant to a defrosted state of the first cooling coil for opening the valve means, second valve means for controlling the circulation of cooling fluid through the second cooling coil, control means responsive to the temperature of the space cooled by the second cooling coil for opening the second valve means upon an increase in space temperature, and means operative upon opening of either valve means for operating the cooling fluid circulating means.

18. In a refrigeration system including a refrigerating apparatus having a first evaporator means for cooling a space wherein defrosting of that evaporator means is desirable, a second evaporator means for cooling another space wherein defrosting of the evaporator means is not re- 17. In a cooling system including a cooling apquired and a common compressor for circulating refrigerant through both evaporator means, the combination with saidapparatus of, valve means on the discharge side of the first evaporatormeans for controlling the circulation of refrigerant therethrough, control means responsive to the pressllre'ln the first evaporator means and to the temperature of the space cooled thereby for opening the valve means upon an increase in space temperature providing the first evaporator means is defrosted, control means responsive to an increase in the temperature in the second space, valve means in control of the fiow of refrigerant through the second evaporator controlled thereby, and means operative upon opening of either valve means for operating the compressor. I

19. In a refrigeration system including a refrigerating apparatus having a plurality of evaporators for cooling a plurality of spaces and a common compressor for circulating refrigerant through all of the evaporators, the combination with said apparatus of, valve means associated with each evaporator for controlling the circulation of refrigerant through its associated evaporator, control means associated with each evaporator and responsive to the temperature of the space cooled thereby for opening the valve means of that evaporator upon an increase in temperature, a valve located in the common discharge from all of the ev-aporators for controlling the circulation of refrigerant through all of the evaporators, control means responsive to the pressure in the evaporators and to an increase in temperature in any of the spaces for opening the valve upon a call for cooling providing all of the evaporators are defrosted.

20. In a cooling system including a cooling apparatus having a plurality of cooling coils for cooling a plurality of spaces and a common means for circulating through the cooling coils a cooling fiuid having sufficient cooling capacity to lower the temperature'of the cooling coils belowfreezing whereby frosting of the cooling coils may occur, the combination with said apparatus of, valve means associated with each cooling coil for controlling the flow of cooling fiuid through its cooling coil, control means associated with each cooling coil and responsive to-the frost condition of its cooling coil and the temperature of the space cooled thereby for opening the valve means of that cooling coil upon an increase in space temperature providing that cooling coil is defrosted whereby individual temperature and defrosting control of each cooling coil is obtained, and means operative upon opening of any of the valve means for operating the cooling fiuld circulating means.

21. In a refrigeration system including a refrigerating apparatus having a plurality of evaporator means for cooling a plurality of spaces and a common compressor for circulating refrigerant through all of the evaporator means, the combination with said apparatus of, valve means on the discharge side of each evaporator means for controlling the circulation of refrigerant therethrough, and control means associated with each evaporator means and responsive to the pressure therein and to the temperature of the space cooled thereby for opening the valve 7 means of that evaporator means upon an increase in space temperature providing that evaporator means is defrosted whereby individual temperature and defrosting control of each evaporator means is obtained, and means operative upon opening of any of the valve means for operating the compressor.

22. In a cooling system including a cooling apparatus having a cooling coil for cooling a space and means for circulating through the cooling coil a cooling fluid having sufilicent cooling capacity-to lower the temperature of the cooling coil below freezing whereby frosting of the cooling coil may occur, the combination with said apparatus of, valve means for controlling the circulation of cooling fiuld through the cooling coil, electromagnetic means for opening and closing the valve means. a switch closed upon opening of the valve means, a first switch, means responsive to decrease and increase in the space temperature for opening and clodng the first switch, a second switch, means responsive to a condition attendant to a defrosted state of the cooling coil for clodng the second switch, a third switch, means responsive to a condition normally attendant to a frosted state of the cooling coil for opening the third switch, means for completing a starting circuit through the first and second switches and the electromagnetic means to open the valve means. and means for completing a maintaining circuit through the first and third switches, the maintaining switch and the electromagnetic means to maintain the valve means open.

23. In a refrigeration system including a refrlgerating apparatus having evaporator means for cooling a space and a compressor for circulating refrigerant through the evaporator means, the combination with said apparatus of, valve means on the discharge side of the evaporator means for controlling the circulation of refrigerant through the evaporator means, electromagnetic means for opening and closing the valve means, a maintaining switch closed upon opening of the valve means, a first switch, means responsive to space temperature for opening and closing the first switch, a second switch, means responsive to the pressure within the evaporator means for closing the second switch when the pressure increases to a predetermined value, a third switch, means responsive to the pressure within the evaporator means for opening the third switch when the pressure decreases to a predetermined low value, means for completing a starting circuit through the first and second switches and the electromagnetic means to open the valve means, and means for completing a maintaining circuit through the first and third switches, the maintaining switch and the electromagnetic means to maintain the valve means open independently of the second switch.

24. In a refrigeration system including a refrigerating apparatus having a plurality of evaporators and a common compressor for supplying refrigerant to said evaporators, the combination with said apparatus of, control apparatus controlling the circulation of refrigerant through one of said evaporators, said control apparatus including means responsive to a condition normally attendant to a defrosted state of said one of the evaporators for always preventing the supply of refrigerant to that evaporator under all conditions of operation until said condition normally attendant to a defrosted condition of the evaporator has been attained, and means controlling thecirculation of refrigerant to the remaining evaporators;

25. In a refrigeration system including a re, frigerating apparatus having a plurality of evap orators and a common compressor or condenser for supplying refrigerant to said evaporators, the combination with said apparatus of, means for controlling the circulation of refrigerant through one of said evaporators, said control means including means responsive to a. condition normally attendant to a defrosted state of said evaporator to always prevent circulation of refrigerant thereto until such condition has been attained, and control means in control of the circulation of refrigerant through another of said evaporators irrespective of whether the same is frosted or defrosted.

26. In a cooling system including a cooling apparatus having a cooling coil for cooling a space and means for circulating through the cooling coil a cooling fluid having sufiicient cooling capacity to lower the temperature of the cooling coil below freezing whereby frosting of the cooling coil may occur, the combination with said apparatus of, valve means for controlling the circulation of cooling fluid through the cooling coil, said valve means being movable between open and closed positions, means for latchin said valve means in one of its positions, means responsive to the temperature of the space and means responsive to a condition normally attendant to a defrosted state of the cooling coil, said condition responsive means being arranged to cause opening of the valve means only upon the attainment of said condition, and said temperature responsive means being arranged to cause closure of the valve means upon the attainment of a predetermined relatively low temperature in the space, one of said responsive means being operatively related to said latch means for causing the valve to move from one of its positions to the other.

2'7. In a cooling system including a cooling apparatus having a cooling coil for cooling a space and means for circulating through the-cooling coil a cooling fluid having suflicient cooling capacity to lower the temperature of the cooling coil below freezing whereby frosting of the cooling coil may occur, the combination with said apparatus of, valve means for controlling the circulation of cooling fiuid through the cooling coil, control means responsive to a condition.- normally attendant to a defrosted state of the cooling coil for opening the valve means only upon the attainment of such condition and means responsive to space temperature for causing the valve means to return to closed position upon the occurence of a predetermined relatively low temperature in the space.

WILLIAM L. McGRA'I'H.

. a CERTIFICATE or CORRECTION. Patent =No; 2,257,261. I April 1,. 191,1. Y WILLIAILL. McGRATH.

It is hereby certified that error appears in the printed specification.

ofltheabove numbered patent requiring correction as follows: Page 2, see-- one column, line 14.5, for "65, and read --65, 66, and-; page 8,'first coiumn, line 70, claim 18, strike out '17. In a cooling system includinga cooling ap-"; page 9, first column, line 12, claim 22, after "condition"- insert --normally--; and that the said Letters Patent shoul'dbe read with this correction therein that the same may conform tothe record of the case in the Patent Office. I I

S igned and sealed this 29th day of July, A. D. 19141.

Henry'Van Arsdale, (Seal) Acting Commissioner of Patents. 

